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As the largest freshwater river flowing through Harbin, the Songhua River is a standby water source. It is very important to know the species and distribution of antibiotic-resistant bacteria (ARB) in the river. In this study, five antibiotics were selected to screen and identify ARB in spring and autumn. The results showed that the concentration of cefotaxime-resistant bacteria was the highest, and the maximum concentration at S6 in spring was up to 1.40 × 104 CFU/mL. In spring and autumn, bacteria resistant to three antibiotics were screened at S1 of the Songhua River, and bacteria resistant to five antibiotics were screened at S6. No multiple antibiotic-resistant bacteria (MARB) were screened in the other four sites in autumn, while MARB were screened in the other three samples except S2 in spring. In all sample areas in spring and autumn, the probability of screening MARB at S1 and S6 was the highest, reaching 100%. The identification results of 16S rDNA polymerase chain reaction (PCR) products of ARB showed that a total of 51 ARB strains from 15 bacterial genera were screened in the Songhua River, of which 20 ARB strains were from Pseudomonas. Among the 15 bacterial genera, bacteria from 8 bacterial genera have pathogenicity. The results of this study revealed the concentration, spatial distribution, and seasonal variation of culturable ARB in the Songhua River, providing data support for the remediation of antibiotic resistance gene (ARG) pollution in the river.

A virtual power plant (VPP) is an effective way to manage distributed energy resources. Virtual power plant cluster (VPPC) is constructed due to the increasing number of VPPs. It has great potential in carbon emission reduction through coordination between VPPs. Therefore, a dynamic dispatch priority model is proposed. The model adjusts the dispatch sequence of VPPs based on carbon emissions. The higher the carbon emissions, the lower the dispatch priority. The VPPC participates in carbon trading and the carbon trading cost is included in the optimization objective. There are still many uncontrolled distributed energy resources, e.g., wind power, out of the VPPC. The distributionally robust optimal method is used to deal with the uncertainty of wind power. Finally, this paper proposes a two-stage distributionally robust optimal model of VPPC considering carbon emission-based dynamic dispatch priority. This model can be solved by the column-and-constraint generation (C&CG) algorithm. A VPPC with four VPPs is used in case studies, which verify the economic benefit and low carbon of the proposed model.

Anti-idiotypic antibody technology has been widely developed. Here, we prepared the F(ab’)2 fragments of the Cry1F toxin polyclonal antibody as Ab1and screened an anti-idiotype nanobody (VHH) for Bt Cry1F toxin from the camelid naive antibody phage display library. After three cycles of panning, six clones were isolated and subjected to indirect competitive enzyme-linked immunosorbent assay (IC-ELISA) for the detection of the Cry1F toxin. A competition inhibition rate of 47.00% exists between the anti-idiotype nanobody with the highest activity (5B) and Cry1F toxin for F(ab’)2 fragments. The binding abilities between the anti-idiotypic nanobody 5B and brush border membrane vesicles (BBMV) of Ostrinia furnacalis (Guenée) are also good. The anti-idiotypic nanobody 5B expressed through the prokaryotic system has the same activity as in phage form, and mortality compared to controls could reach 23.3% (P

Microcystin-LR (MC-LR) is one of the most worldwide harmful cyanobacterial toxins. A lots of antibodies against MC-LR have been generated and characterized. However, the knowledge about the epitopes of MC-LR was still limited. The objective of this study was to analyze the epitopes of MC-LR and demonstrate the binding mode of MC-LR with its antibody. The variable genes of a mouse hybridoma cell line (Mab5H1–3B3) raised against MC-LR have been cloned and assembled in a single chain variable fragment (scFv), and then soluble expressed in E.coli BL21. Based on the scFv, the IC50 and IC10 for MC-LR were determined to be 7.45 nM and 0.30 nM by competitive ELISA. And the scFv also showed 115% and 112% cross-reactivities to MC-RR and MC-YR, and 59% to MC-LA. By molecular docking, the binding mode between MC-LR and its scFv was demonstrated. A hydrogen bond interaction was observed between the carbonyl group of Adda5 residue of MC-LR and its scFv, and the guanidyl group of Arg4 residue and phenyl group of Adda5 residue of MC-LR were also involved in the interaction. These predicted epitopes were supported by antibody cross-reactivity data. By comparing the antibody informatics of MC-LR scFv with its predicted paratopes, VH-CDR1 was crucial for MC-LR binding, and its specificity could be tuned by engineering in Vκ-CDR1 and Vκ-CDR3. These information would be useful for the hapten design for microcystins or improving the properties of MC-LR scFv in vitro.

Vancomycin (Van) is a common antibiotic that pollutes food, feed and ecological environment. In the present study, an anti-Van polyclonal antibodies (pAbs) and Eu3+-labeled goat anti-rabbit IgG monoclonal antibody based indirect competitive time-resolved fluoroimmunoassay (IC-TRFIA) was established for ultrasensitive determination of Van, and its half-maximum inhibition concentrations (IC50) was 13.74 ng/L and the limit of detection (LOD) was 1.07 ng/L. The IC-TRFIA showed strong cross-reactivity (CRs) of 36.2% for norvancomycin, and less than 0.1% for polymyxin B, kanamycin and ampicillin. It was found that the IC-TRFIA for Van spiked in different milk powder samples determination were with good accuracy, stability and repeatability, and its recoveries are 83.0–97.9%, also with its coefficient of variations (CVs) are 3.0–12.9% in intra-assay and inter-assay. The results showed that the established IC-TRFIA was promising for ultrasensitive determination of Van in food samples. Highlights Prepared high-quality Van-KLH/BSA conjugates. Obtained high activity and purify anti-Van polyclonal antibodies. Prepared high-quality Eu3+-labelled goat anti-rabbit IgG monoclonal antibody. Firstly established an IC-TRFIA for Van based on the anti-Van polyclonal antibodies and Eu3+-labelled goat anti-rabbit IgG monoclonal antibody. The IC-TRFIA can be used for ultrasensitive determination of Van in milk powder samples.

Here, we firstly reported to generate panels of anti-idiotypic single-chain variable fragments (scFvs) of Bacillus thuringiensis Cry2Aa toxin by chain shuffling method. Light- and heavy-chain-shuffled libraries based on two parental clones were constructed. The signal of the light-chain-shuffled library was 4.2-fold higher than the heavy one. Solely after one round panning, eight mutants were rapidly isolated from the chain-shuffled libraries. The apparent affinity of the best clones was 2.65 × 106 M−1, a 2.59-fold improvement over the parental clone. The binding abilities between anti-idiotypic scFvs with brush border membrane vesicle of Plutella xylostella larvae were also determined. This work demonstrated that chain shuffling could rapidly generate panels of antibodies with similar binding abilities but of the distinct idiotypic composition. The serials of mutants can be used to map the binding epitope of the receptors in target insects instead of Cry2Aa toxin.